The IEEE (Institute of Electrical and Electronics Engineers) 802.11 family of standards (including IEEE 802.11, 802.11a, 802.11b, 802.11g and 802.11n) specify over-the-air interfaces in a wireless LAN (Local Area Network), e.g., between a wireless client and a base station or another wireless client. The IEEE 802.11 standards place specifications on the parameters of both the physical (PHY) and medium access control (MAC) layers of the network. The PHY layer, which handles the actual transmission of data between nodes, may use direct sequence spread spectrum (DSSS), frequency hopping spread spectrum (FHSS), or infrared (IR) pulse position modulation. The MAC layer uses a set of protocols to manage and maintain communication between 802.11 clients/stations by coordinating access to the shared wireless medium. The MAC layer is responsible for performing a number of functions including scanning, authentication, and association.
The IEEE 802.11g standard specifies fixed PHY (Physical Layer) overheads for each data packet regardless of packet size or data rate. Therefore, the percentage of PHY overhead with respect to packet duration is larger for packets with fewer data bits or a higher PHY data rate. Furthermore, the percentage of PHY overhead (with respect to the transmission time for a data packet) may increase for the next generation wireless LANs. For example, the proposed IEEE 802.11n specification (directed to high throughput wireless LANs) seeks to improve the PHY data rate by a factor of three or four, but the preamble and signal fields in the header will still be transmitted at low data rates for high reliability. As a result, the transmission time for each data packet will become small, increasing the percentage of PHY overhead.